fix(modules/iam-role): missing json encoding step for assume role policy

modules/iam-role/main.tf

@@ -1,7 +1,7 @@
 resource "aws_iam_role" "this" {
   name               = var.name
   description        = var.description
-  assume_role_policy = var.assume_role_policy
+  assume_role_policy = jsonencode(var.assume_role_policy)
 
   tags = var.tags
 }